Switching mechanism



May 10, 1966 c, ROBBINS ET AL 3,250,883

SWITCHING MECHANISM Original Filed Feb. 19. 1957 United States Patent 11 Claims. (Cl. 200-159) This is a division of copending application Serial No. 641,177, filed February 19, 1957.

This invention relates to enclosed, externally actuated spring return switching mechanisms and more particularly to relatively flat switching mechanisms adapted for mounting to an electrical device.

While not limited thereto, the invention is especially adapted for mounting to and for operation by a pilot light device of the pushbutton type.

An object of the invention is to provide an improved switching mechanism;

A more specific object of the invention is to provide a flat switching device operable by an external actuator.

Another specific object of the invention is to provide an improved switching device of the self-enclosed type having normally open and normally closed contacts adapted for operation by a member which might be subject to overtravel.

Another object of the invention is to provide an improved switching device which is simple in construction and reliable in operation and occupies a small amount of space.

A further object of the invention is to provide an improved switching device especially adapted for mounting to a pushbutton test device.

Other objects and advantages of the invention will hereinafter appear.

These and other objects and advantages of the invention and the manner. of obtaining them will best be understood by reference to the following description of an embodiment of a switching mechanism taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a top plan view of the switching mechanism or switch unit with cover removed to illustrate details;

FIG. 2 is a sectional view of the switch unit with cover replaced taken along line 2 2 of FIG. 1;

FIG. 3 is a bottom plan View of the switch unit;

FIG. 4 is a sectional view of the switch unit taken along line 4-4 of FIG. 3; and

FIG. 5 is a top plan view of the switch unit showing an alternate form of electrical connection that can be employed therewith.

Referring to FIGS. 1 to 5, there is shown a switching mechanism or switch unit 38 constructed in accordance with the invention. The numeral 70 design-ates a one piece, molded, phenolic insulating base which is provided with a diagonally disposed, integrally formed lateral projections undercut from the bottom to provide reduced thickness wherein are provided openings 70a and 7%, respectively, to accommodate assembly screws. These projections are further provided with-smaller openings 70c and 7tld, adapted to accommodate rivets 71 and 72, respectively, which secure an insulating cover 73, prefer- 3,250,883 Patented May 10, 1966 ably formed of paper based phenolic material, to the upper side of switch base (FIG-S. 2 and 4). Referring to FIGS. 2 and 4, one end of a helical compression spring 74 is located in a recess or deeper cavity within an integrally formed projection extending from the lower surface of switch base 70. The other end of said spring extends into an elongated recess or chamber 70 within the main body portion of switch base 70 and bears against .the bottom surface of a substantially rectangular contact bridge contained therein. Contact bridge 75, preferably punched or stamped from sheet brass, is provided with an integrally formed contact portion 75a near its center which, as FIGS. 1 and 2 show, extends transversely relative to the length of said bridge and ter minates in projections on either side of said contact bridge. As most clearly shown in FIGS, 2 and 4, this transverse contact portion 75a is provided by a raised rib or inverted U-shaped portion formed across the bridge. These projections, by engaging the sides of the recesses wherein they lie as shown in FIG. 2, limit the longitudinal travel of the contact bridge, that is to say, they prevent the extreme ends of contact bridge 75 from touching or scraping the ends of longitudinal recess 70f wherein it lies. FIGS. 1 and 3 show that one end of contact bridge 75 is provided with an integrally formed ridge which insures that downward pressure on said bridge by a push bar is always applied at the same point, the base and cover being adapted for receipt of one end of a push bar through a hole 73a in the cover and an aperture 7% opening into recess 70 A common contact plate 76 preferably formed of brass and having a shape of a parallelogram, lies in a shallower recess which is disposed athwart and is partially coextensive with recess 70] in which contact bridge 75 is disposed (FIGS. 1 and 2). Contact plate 76 is welded, brazed or otherwise electrically connected to the bare end of conductor 37 which extends through a groove to one edge of the base and is adapted to be connected to a terminal of an external circuit or device. place in its recess by the action of insulating cover 73 at tached to switch base 70.

Normally, biasing spring 74,'bearing against the lower surface of contact bridge 75 slightly to one side of the midportion or between the contact portion formed therein and its actuated end, forces this bridge upward so that its contact portion 75a between the lateral projections bears against contact plate 76 and so that the end of contact bridge 75, which contains the bridge, is in electrical contact with the lower surface of a contact 77 carried in a recess formed in the upper surface of switch base 70. Contact 77 is secured by a rivet 77a which extends through switch base 70 and acts to secure a terminal plate 77b within a recess formed in the lower surface of said switch base. Terminal plate 77b is provided with a steel terminal screw and a steel terminal lug such as a saddle clamp.

When the push bar, which is adapted to extend into recess 7 (if in switch base 70 through the opening 73a in the insulating cover 73 and through aperture 70a forces one end of contact bridge 75 downwardly against spring 74, electrical contact between bridge 75 and contact 77 is broken. The bottom of the base is provided with an opening extending from near spring 74 to the actuated end of bridge 75 to provide clearance for contact bridge 75 when it is depressed by an operating plunger. The other Contact plate 76 is held in end of contact bridge 75, however, moves upwardly into contact with another portion of cont-act plate 76 and into contact with the lower surface of a contact 7 8 carried in a recess formed in the upper surface of switch base 70. The contact 78 is secured by a rivet 7 8a which extends through switch base 70. Rivet 78a also acts to secure a terminal plate 78b within a recess formed in the lower surface of the switch base. Terminal plate 78b is provided with a steel terminal screw and a steel terminal lug such as a saddle clamp and is adapted to be connected to a line conductor.

If contact bridge 75 is depressed to such an extent that electrical contact between raised contact portion 75a and contact plate 76 is broken, electrical contact still exists between members 75, 76 and 78 at the other end of bridge 75 as hereinbefore explained;

When the pushrod is released and ceases to force contact bridge 75 downward, contact bridge 75 is forced back into its normal position by spring 74 thereby causing" electrical contact between it and contact 73 to be broken and electrical contact between it and contact 77 to be reestablished.

While the device hereinbefore described is effectively adapted to fulfill the objects stated, it is to be understood that we do not intend to confine our invention to the particular preferred embodiment of switching mechanism disclosed, inasmuch as it is susceptible of various modifications without departing from the scope of the appended claims.

We claim:

1. In a switch adapted for use with an electrical device having a movable member, in combination:

an insulating housing having a chamber;

a pair of stationary contact members Within said chamber having terminals outside of said housing;

a contact plate within said housing, said plate adapted to be electrically connected to said device;

a movable conductive member within said housing adapted for rocking on said plate to engage said contact member alternately;

and biasing means disposed between said movable conductive member and a wall of said chamber, said biasing means maintaining said movable conductive member in electrical engagement with said plate while permitting movement of said conductive member out of engagement with said one of said stationary contact members and into engagement with the other of said stationary contact members upon movement of said movable member of said device.

2. A fiat, spring-return switch adapted for mounting on an electrical device comprising:

a substantially flat insulating base having an elongated cavity therein provided with a deeper cav ty olfset from its center;

an elongated movable cont-act in said elongated cavity;

a pair of stationary contacts secured in shallow recesses in said base to overlie opposite end portions of said movable contact;

a common contact member lying in a shallow recess athwart said movable contact;

a raised contacting portion on said movable contact below said common contact member;

and a compression spring in said deeper cavity biasing said movable contact into engagement with said common contact member and the stationary contact nearer to said compression spring.

3. The invention defined in claim 2, together with:

a flat cover secured on top of said base for retaining said common contact member in its recess;

and an aperture in said cover adapted to receive an actuator for depressing said movable contact out of engagement with said stationary contact nearer said spring and into engagement with the other stationary contact.

4. The invention defined in claim 2, together with:

a groove in the upper surface of said base leading from one end of said common contact member to an edge of the base adapted for receiving an electrical conductor.

5. The invention defined in claim 4, wherein said base comprises:

a hole extending from the other end of said common contact member through the bottom of said base adapted for receiving an electrical conductor for an alternative connection to said common contact member.

6. The invention defined in claim 2, wherein said movable contact comprises:

lateral projections extending in opposite directions from said raised cont-acting portion;

and lateral grooves in the opposite sides of said elongated cavity for guiding said projections to maintain the ends of said movable contact clearof the end walls of said elongated cavity.

7. The invention defined in claim 2, wherein said movable contact comprises:

a raised portion at the end thereof below the cover aperture for insuring that the depressive force is applied to said movable contact always at the proper point.

8. In a switch having normally-closed and normallyopen contacts and adapted for use with an operating member which might be subject to overtravel, the combination comprising:

an insulating housing having a cavity therein;

a pair of spaced stationary contacts partially extending into said cavity; common contact at least partially overlying said cavity and adapted to be connected to an electrical device;

a movable contact in said cavity having an intermediate contacting portion and opposite end contacting portions spaced therefrom;

resilient spring normally pressing said intermediate contacting portion and one end contacting portion of said movable contact into bridging engagement with one of said stationary contacts and said common contact to complete a normally-closed electrical connection therebetween and for normally maintaining the other end contacting portion of said movable contact separated from the other'stationary contact;

and an opening in said housing adapted for receiving a depressible operating member to open said normally closed connection and to cause the other end contacting portions of said movable contact to be pressed by the force of said spring into bridging engagement between said other stationary contact and said common contact thereby to insure that the normally-open contacts remain closed in the event overtravel of the operating member causes said intermediate contacting portion to separate from said common contact against the force of said spring.

9. The invention defined in claim 8, wherein said intermediate contacting portion comprises:

a raised portion on said movable contact normally engaging said common contact and pivoting thereon through part of the stroke when said one end contacting portion is depressed by the operating member.

10. The invention defined in claim 8, together with:

grooves in the opposite sides of said cavity in said housing;

and said intermediate contacting portion comprising a raised portion for engaging and pivoting on said comon contact and having lateral extensions held in said grooves to maintain said movable contact clear of the ends of said cavity throughout the entire stroke.

3,250,883 5 6 11. The invention defined in claim 8, wherein said member adapting it for connection to an external common contact comprises: circuit.

a flat conductive member arranged athwart said movable contact for engagement by said intermediate References Cited by the Examiner common contact and having lateral extensions held 5 UNITED STATES PATENTS tinfsaidmvab1eContact; 2,614,194 10/1952 Lester 20o 15 and said housing comprises openings leadlng from opposite diagonal portions of said fiat conductive ROBERT K. SCHAEFER, Primary Examiner. 

1. IN A SWITCH ADAPTED FOR USE WITH AN ELECTRICAL DEVICE HAVING A MOVABLE MEMBER, IN COMBINATION: AN INSULATING HOUSING HAVING A CHAMBER; A PAIR OF STATIONARY CONTACT MEMBERS WITHIN SAID CHAMBER HAVING TERMINALS OUTSIDE OF SAID HOUSING; A CONTACT PLATE WITHIN SAID HOUSING, SAID PLATE ADAPTED TO BE ELECTRICALLY CONNECTED TO SAID DEVICE; A MOVABLE CONDUCTIVE MEMBER WITHIN SAID HOUSING ADAPTED FOR ROCKING ON SAID PLATE TO ENGAGE SAID CONTACT MEMBER ALTERNATELY; AND BIASING MEANS DISPOSED BETWEEN SAID MOVABLE CONDUCTIVE MEMBER AND A WALL OF SAID CHAMBER, SAID BIASING MEANS MAINTAINING SAID MOVABLE CONDUCTIVE MEMBER IN ELECTRICAL ENGAGEMENT WITH SAID PLATE WHILE PERMITTING MOVEMENT OF SAID CONDUCTIVE MEMBER OUT OF ENGAGEMENT WITH SAID ONE OF SAID STATIONARY CONTACT MEMBERS AND INTO ENGAGEMENT WITH THE OTHER OF SAID STATIONARY CONTACT MEMBERS UPON MOVEMENT OF SAID MOVABLE MEMBER OF SAID DEVICE. 